1. Field of the Invention Vehicle
The present invention relates to a frame structure of a seat back for a vehicle and a seat back for a vehicle with such a frame structure, in particular, relates to the frame structure of the seat back for the vehicle and the seat back for the vehicle with the frame structure which is capable of securing a strength of the seat back in a sheet for the vehicle, while at the same time decreasing the weight of the seat back.
2. Discussion of the Related Art
Conventionally, the sheet for the vehicle including a sheet cushion the lower portion of which is fixed to a floor portion of a vehicle compartment and a seat back the lower portion of which is supported by a rear portion of the sheet cushion has been used. With respect to the type of the seat back, there have been two types, one is a seat back which can be forwardly inclined and the other is a seat back which cannot be forwardly inclined so that it is maintained upright.
Such a seat back for the vehicle includes a seat back frame which comprises a panel frame in a plane form with a substantially rectangular shape and a framework disposed to be along a peripheral edge of the panel frame, and a pad covering the seat back frame and a trim for an outer skin, etc. are provided on the seat back frame.
As shown in FIG. 8, the seat back for the vehicle has been divided into two parts, each of which includes a structure in which a pipe product and a pressed product are assembled. In this connection, FIG. 8 shows one of the divided frameworks. For instance, with respect to the framework of the seat back for a rear seat which constitutes a leaning portion, as shown in FIG. 8, the seat back is supported at the three points, two of which are side portions of the lower section, and one of which is a door side of the upper section. As shown in FIG. 9, mainly from a technical point of view which is related to securing a torsion stiffness, a pipe member A with a closed cross-section is adopted as a structural member. The pipe member A is worked by a bending process so as to be shaped into a configuration which can be disposed to be the peripheral edge of the panel frame. On the other hand, in order to fix the seat back for the vehicle to a vehicle body via the pipe member A at the three respective points, a bracket member B as a pressed member is fixed to the pipe member A by welding.
In addition, as regulated by ECE (Automobile Regulation), in order to increase a maximum tolerant load which is applied to the rear seat due to a displacement of a luggage in a rear luggage compartment, the seat back for the rear seat extending at the substantially central portion of the panel frame and on which a reinforcing frame, both ends of which are fixed to the framework by welding, is disclosed by Japanese Patent Laid-open Publication 2003-235672, for instance.
By providing such a reinforcing frame, since the reinforcing frame is formed in such a way that an intermediate portion of the reinforcing frame extends through a portion on which an external force is exerted and both ends of the reinforcing member are connected to the framework including a high strength, dents on the panel frame can be prevented from being generated due to the fact that the intermediate portion of the reinforcing frame absorbs the external force generated by the displacement of the luggage, whereby its strength against the large load applied on an external force receiving portion can be improved.
However, such a structure has the following technical problems.
That is to say, recently, much attention has been paid to a decrease in the amount of fuel consumption, in view of the prevention of global warming, so that an effort has been made to improve an engine's performance and to decrease the weight of the automobile.
From the above points of view, the above structure adopts duplicate members, so that there is a room for further decreasing the weight of the automobile.
Conventionally, in the case of the seat for the vehicle, it was fixed to the necessary position of the vehicle body by adopting a steel tube as a strength member, while appropriately providing a bracket at the necessary position. More specifically, a bracket including a plane portion which is separately manufactured by a press is fixed on an outer surface of the pipe member by welding, so that an excessive member was adopted, from the technical point of view related to securing the necessary strength. This is contrary to decreasing the weight of the automobile. In particular, as described above, in case of the seat back for the rear seat, it is even more so when the reinforcing frame is adopted.